Download Atoms and the Periodic Table

Atoms and the
Periodic Table
Chapter 4
1
Atomic Structure
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Atoms are the simplest unit
of a substance that still
maintain the properties of
the substance.
John Dalton proposed that
atoms could not be divided.
Dalton also stated that
atoms of different elements
could join to form
compounds.
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Parts of an Atom
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Atoms are composed of
subatomic particles.
Protons and neutrons
are found in the
nucleus of the atom.
Electrons are found in
orbitals around the
nucleus of the atom.
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Protons
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Protons have a positive
charge.
Protons have the mass of
one amu (atomic mass
unit).
The number of protons in
an atom is characteristic of
that element.
Each element has different
number of protons.
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Neutrons
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Neutrons have no
charge.
Neutrons have the
mass of one amu.
Neutrons add to the
mass of an atom.
Atoms of the same
element with different
number of neutrons
have different masses
(isotopes).
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Electrons
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Electrons have a negative
charge.
Electrons have the mass of
1/2000 the mass of a
proton.
The mass of an electron is
insignificant.
The outer most electrons
determine how elements
combined in chemical
compounds.
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Quarks
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A quark (IPA: /kwɔrk/) is a generic
type of physical particle that forms
one of the two basic constituents
of matter, the other being the
lepton.
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Various species of quarks
combine in specific ways to
form protons and neutrons, in
each case taking exactly three
quarks to make the composite
particle in question.
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Models of Atoms
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Niels Bohr suggested that
electrons in an atom
move in set paths around
the nucleus.
Electrons can only be in
certain energy levels.
Number of electrons=2n2
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Electron Cloud Model
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This model suggest that
electrons orbit the
nucleus in a cloud.
The regions in an atom
where electrons are
likely to be found are
called orbitals.
The four different kinds
of orbitals are the s, p,
d and f orbitals.
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Valence Electrons
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An electron in the
outermost energy level
of an atom is called a
valence electron.
Valence electrons
determine an atom’s
chemical properties and
its ability to form bonds.
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Periodic Table
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The Periodic Law
states that when
elements are arranged
this way, similarities in
their properties will
occur in a regular
pattern.
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Structure of the Periodic Table
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Horizontal rows in the
periodic table are called
periods.
Atoms of elements in
the same group, or
column, have the same
number of valence
electrons, so these
elements have similar
properties.
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Ions Formation
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Atoms that gain or lose
electrons form ions.
Elements that lose
electrons have a
positive charge (cation).
Elements that gain
electrons have a
negative charge
(anion).
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Periodic Information
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The atomic number is
the number of protons
in an element.
The mass number of an
atom equals the
number of protons plus
the number of
neutrons.
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Isotopes
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Isotopes are atoms of
the same element that
have different number
of neutrons.
Isotopes of the same
element have different
atomic masses.
The three isotopes of
hydrogen are protium,
deuterium & tritium.
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Mass of Atoms
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An atomic mass unit (amu)
is equal to one-twelfth of the
mass of a carbon 12 atom.
The average atomic mass
for an element is a weighted
average, so the more
commonly found isotopes
have a greater effect on the
average than rare isotopes.
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Squares on the Periodic Table
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The chemical symbol is
abbreviation of the
chemical name.
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The first letter of the
chemical symbol is
capitalized.
If there is more than one
letter, the other letters
are lower case.
Atomic number.
Average atomic mass.
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Classifications of Elements
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Metals are on the left
side of the periodic
table.
Nonmetals are on the
right side of the periodic
table.
Metalloids are located
between the metals
and nonmetals.
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Alkali Metals
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This is the most
reactive group of
metals.
Has only 1 valence
electrons.
Reacts violently with
water.
Elements include Li,
Na, K, Rb, Cs & Fr.
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Alkaline Earth Metals
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Not as reactive as Alkali
Metals.
Has two valence
electrons.
Members include Be,
Mg, Ca, Sr, Ba & Ra.
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Transition Metals
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Members have a wide
variety of properties.
Has 1, 2 or 3 valence
electrons.
Contain the coin
metals: gold, silver &
copper.
Contain the iron triad of
Fe, Co & Ni.
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Halogens
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The most reactive
group of nonmetals.
Has 7 valence
electrons.
All members are
poisonous.
Members include F, Cl,
Br, I & At.
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Noble Gases
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Members contain a
stable octet with 8
valence electrons.
These elements do not
react with other
elements. Don’t form
compounds.
Members include He,
Ne, Ar, Kr, Xe & Rn.
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Semiconductors
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Have the properties of
both metals &
nonmetals.
Used in the electronic
industry.
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Using Moles to Count Atoms
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A mole is a collection of
a very large number of
particles.
Avagadro’s constant is
the number of particles
in a mole of a pure
substance.
Avagadro’s constant is
6.022 x 1023/mol.
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Molar Mass
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Molar mass is the mass
in grams of 1 mol of a
substance.
The molar mass of an
element in grams is the
same as its average
atomic mass in amu on
the periodic table.
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Converting Moles to Grams
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Amount(mol) x molar mass of element/1 mol of element = mass(g)
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Amount(mol)=1 mole of element/molar mass of element x mass(g)
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Converting Amount to Mass
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Determine the mass in grams of 5.50 mol of
iron.
Given: amount of iron=5.50 mol mol Fe
molar mass of iron=55.85 g/mol Fe
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Unknown: mass of iron=?g Fe
55.85 g Fe/1 mol Fe
5.50 mol Fe x 55.85 g Fe/1 mol Fe=307 g Fe
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Converting Mass to Amount
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Determine the amount of iron present in 352
g of iron.
Given: mass of iron=352 g Fe
molar mass of iron=55.85 g/mol Fe
Unknown: amount of iron=? mol Fe
1 mol Fe/55.85 g Fe
352 g Fe x 1 mol Fe/55.85 g Fe=6.30 mol Fe
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Sample Problem 1
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A chemical reaction requires 5.00 mol of
sulfur as a reactant. What is the mass of this
sulfur in grams?
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160.4 g S
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Sample Problem 2
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For an experiment you have been asked to
do, you need 1.5 g of iron. How many moles
of iron do you need?
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0.027 mol Fe
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Sample Problem 3
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James is holding a balloon that contains 0.54
g of helium gas. What amount of helium is
this?
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0.14 mol He
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Sample Problem 4
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A pure gold bar is made of 19.55 mol of gold.
What is the mass of the bar in grams?
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3851 g Au
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Sample Problem 5
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Robyn recycled 15.1 mol of aluminum last
month. What mass of aluminum in grams did
she recycle?
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407 g Al
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